Filters are generally used to remove one or more contaminants from a stream of fluid, including gas and liquid. For example, a bank of filters may be provided in a gas filtering system upstream of a gas turbine in order to remove contaminants from a stream of fluid being supplied to the gas turbine. Over a period of time the filters become loaded with contaminants that have been removed from the stream of fluid by the filters. When the contaminant buildup on the upstream side of the filters causes the fluid flow through the filters to be restricted by a predetermined amount, the filters are typically replaced or cleaned.
Some gas filtering systems may utilize self cleaning of the filters to periodically remove contaminants from the filters. Such self cleaning systems may utilize pulse back cleaning to periodically discharge bursts of air into the filters in an opposite direction from the typical flow of fluid, thereby causing reversal of the fluid flow moving through the filters and a sudden change in pressure causing the removal of contaminants accumulated on the upstream side of the filters. The dislodged contaminants may be drawn into a secondary cleaning air circuit on the upstream side of the filters to minimize re-entrainment of the dislodged contaminants back into the filters. The pulse back cleaning decreases the amount of contaminants on the upstream side of the filters and resultantly reduces the amount of restriction of the fluid flow. The pulse back cleaning accordingly reconditions the filters for continued, substantially uninterrupted service and increases the interval for servicing the filters. One such gas filtering system that utilizes a bank of filters and pulse back cleaning is the ASC III Intake Filter System available from AAF International of Louisville, Ky.